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Reflectivity and velocity displays of the first tornadic storm captured with the NWRT
Phased Array Radar
“It'll pay back many times in protecting the citizens of the U.S. ” - Doug Forsyth
Phased Array radar is NSSL's newest radar frontier. The Phased Array radar has a unique antenna that can collect the same amount of information as a conventional radar, but in about one-sixth the time. Researchers believe phased array radar could expand warning lead times from 10 minutes to 18-22 minutes. The radar's electronic beams can also be directed at certain elements of a storm, giving weather forecasters much more accurate and complete data than the current NEXRAD system. The new technology will also gather storm information not currently available, such as rapid changes in wind fields to provide more thorough understanding of storm evolution. Researchers and forecasters can then improve conceptual storm models and use that knowledge to evaluate and improve stormscale computer models.
A successful partnership
The Phased Array radar project
is the successful result of a partnership including NOAA's NSSL and NWS,
Lockheed Martin, U.S. Navy, Federal Aviation Administration, Basic Commerce
and Industries, Inc., the Oklahoma State Regents for Higher Education,
and the University of Oklahoma's School of Meteorology and College of
Engineering.
The history of Phased Array radar
Navy ships originally used phased array radar technology to protect naval
battle groups from missile threats. Scientists believe the same technology
has great potential for increasing lead time for tornado warnings.
In 2000, the Navy agreed to loan an antenna to NSSL and provided $10,000,000
in funding to help build the National Weather Radar Testbed (NWRT).
The NWS provided the transmitter and additional funding from NOAA, OU,
Lockheed Martin, and OSRHE purchased the environmental processor. In addition,
the FAA provided initial funding for research, program management and
initial upgrades, and the NWS has donated equipment. The NWRT became
operational in September 2003, and first data were collected in May
2004. Several data sets were collected during the limited 2005 storm
season.
How does phased array work?
Currently
a WSR-88D radar transmits one beam of energy at a time, listens for the
returned energy, then mechanically tilts up a little higher, and samples
another small section of the atmosphere. When it has sampled the entire
volume of atmosphere in that section, the radar goes back down, moves
over a little, and starts the process over again. This continues until
the radar has scanned the entire atmosphere, taking around six or seven
minutes. Phased arrays use multiple beams, sent out at one time, so the
antennas never need to tilt. Scanning takes only 30 seconds, and it already
has dual-polarization capabilities.
Advantages of PAR
- 20 second volume scan rates versus 5-7 minutes
- Dwell – the ability to repeatedly sample areas of interest
- Adaptive scanning – phased array gives us the capability to be able to go back quickly and look at something that draws our attention. This will give us a greater chance of improving the lead times across the nation for severe weather warnings.
- Direct measurements of cross beam winds
- Graceful degradation – lower failure rate
- Multi-mission capability to enable partnerships with diverse mission interests – FAA, NAVY, USAF, Army, Homeland Security
Benefits of Phased Array radar:
- To meteorologists:
PAR technology has the potential to provide high resolution, high quality, dual-polarized data that will increase fundamental understanding of storm evolution, in turn leading to improved computer models, more accurate forecasts and earlier warnings.
- To hydrologists:
Receiving dual-pol data from the PAR in a fraction of the time adds precious minutes to lead warning times for the risk of flash flooding, our country's #1 severe weather hazard.
- To aviation:
The potential to use PAR to track aircraft and identify those that are hostile would prove to be invaluable for homeland security. This would encourage cost offsetting partnerships with the FAA, DOD and Homeland Security.
- To the public:
PAR could increase the average lead time for tornado warning well beyond the current average of 11 minutes.
PAR has potential to provide revolutionary improvements in NWS tornado, severe storm, and flash flood warnings.
CURRENT RESEARCH PROJECTS
- Demonstrate PAR technology can be applied to the tornado detection, forecast, and warning mission in a multi-use environment.
- Demonstrate skill in probabilistic forecasts of tornadoes and other severe weather events using ensembles of models that assimilate PAR data
- Determine if there is a viable economic strategy which would permit a national PAR network to support NOAA, DOT/FAA, DOD, Homeland Security and other national missions.
Remote PAR operations
One goal of the NWRT
facility is to allow scientists at NSSL and across the nation to remotely
operate the phased array radar to collect data in support of their
research. A new Radar Control Interface (RCI) is being developed to simplify
radar control and data collection operations.
Aircraft tracking processor
The PAR is capable of dual-use – it
can do several tasks at once – such as tracking aircraft and scanning weather.
NSSL has been exploring the PAR aircraft tracking capabilities and found
that the PAR aircraft tracks were consistent with data obtained from air
traffic control reports for flights into and out of Will Rogers Airport
in Oklahoma City, OK.
- Beam multiplexing (to improve scanning speed)
- Pulse compression
- Electronic beam steering
FUTURE GOALS
Multi-function Phased Array Radar (MPAR)
Under the leadership
of the National Severe Storms Laboratory, an ambitious plan is currently
being formulated to transition from a multitude of radar systems, used
for aircraft surveillance and weather observations, to a single, multi-function,
phased array radar (MPAR). Significant cost savings are anticipated in
addition to increased functionality.
Preliminary cost savings (are these real numbers?)
- Replace 506 radars with 300 radars at $10M each
- Initial procurement savings is $2 billion
- Lifecycle maintenance cost savings is 1-2 billion
- Graceful degradation - little unscheduled maintenance
- reliability increase 90-95% to 99%
